Radio frequency amplifier



Aug. 25,v 1953 w. A. cLAPs RADIO FREQUENCY AMPLIFIER 2 Sheets-Sheet l Filed Jan. 16, 1950 Auld!) Aug. 25, 1953 w. A. cLAPs RADIO FREQUENCY AMPLIFIER 2 Sheets-Sheet 2 Filed Jan. 16, 1950 QW/0 i;

Patented Aug. 25, 1953 RADIO FREQUENCY AMPLIFIER William A. Claps, Chicago, Ill., assigner to Anchor Radio Corporation, Chicago, Ill., a corporation of Illinois Application January 16, 1950, Serial No. 138,897

(Cl. Z50-16) 19 Claims.

This invention relates to high frequency preampliiiers, particularly a vacuum tube type preamplifier which is intended for use on frequencies encountered in the television spectrum. In. its more specific aspects the present invention is especially concerned with a television preamplifier that uses a movable core tuner arrangement.

It is one of the objects of the present invention to provide a preamplifier that is to be used for amplification of frequencies in each of a number of frequency bands selectively, and wherein the arrangement is such as to permit the use of leads of minimum length to and from the Vacuum tube of the amplifier as the vacuum tube is switched for amplification from one frequency band to another.

In the construction of multi-band amplifiers operating at frequencies with which the present invention is particularly concerned, is customary to utilize separate sets of tuned circuits for each band within the range involved. Thus, in a conventional television receiver equipped with a high frequency amplifier, commonly termed an R. F. or preamplifier, provision is made for the amplication of frequencies in each of two or more bands or channels. Separate tuned circuits are provided for the respective channels, each of which circuits is tunable over its range. Since each tuned circuit requires an amplifying vacuum tube it is customary to provide the respective tunable circuits with a single amplifying vacuum tube, or set of tubes, and to provide switching means for selectively connecting the same vacuum tube amplifier in any selected one of the tuned circuits. In the case of a tuned circuit operating at the frequencies here involved and wherein the tuning is obtained by shifting the position of a movable magnetic core, there is necessarily appreciable spacing between the coils that are tuned by the core or cores in the different frequency bands. Where a switching arrangement is to be provided for connecting the vacuum tube amplifier to selected ones of the tunable coils the leads between one or more of the spaced coils and the switch that effects the connection must be of a considerable length, that is, at least of a length such that produces objections in the tuned circuit. It is an object of the present invention to provide a structure wherein the lengths of these leads may be reduced to a minimum. In accordance with the preferred embodiment of the present invention the vacuum tube amplifier and some of its circuit components are mounted on a movable section of a switch assembly, which section moves from one position to another to connect the vacuum tube amplifier to desired ones of the different frequency band tuners.

It is a further object of the present invention to arrange two or more sets of permeability tuned radio frequency coils in such relationship that a single magnetic core can be moved selectively in one or the other of the coils to effeet the necessary tuning thereof. It is a still further object of this invention to provide such sets of coils with shields between them. In accordance with this feature of the present invention a radio frequency amplifier is provided with tube and circuit components which produce the proper direct current and radio frequency impedances preferably mounted on a moving sectional switch assembly for simple uniform band switching of two or more frequency ranges each having as its tuning components two or more tuning coils to provide for two or more corresponding frequency bands. The two or more tuning coils are mounted on a single sleeve or hollow form to allow changes of the inductance of either of the coils by a straight line motion of a single iron core passing rst through one or" the coils and then continuously on through the next coil or coils in order. The frequency coverage per coil is determined by the diameter of the coil, and the actual center frequency per band is controlled by the length of the wire per coil. The tunable coils for the respective frequency bands are spaced from one another for isolation, and a metal grounding shield is placed between adjacent coils to increase the isolation.

As previously stated, the amplifier tube and circuit components which produce the proper impedances, such as the tube Socket, coils, resistors, and capacitators for the tube are mounted di rectly on the movable switch member that connects the amplifier tube to the desired frequency range tuned coil. This circumvents the need for other intercomponent wiring for the different frequency bands thereby excluding the possibility of variations in wiring under ordinary production methods, and further providing for equal performance of the radio frequency amplifier, oscillator or mixer stage for each band covered.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawings forming a part thereof.

In the drawings:

Figure l is a schematic circuit diagram of an amplier of the present invention;

Figure 2 is an enlarged schematic view show ing one movable portion of the circuit of Figure 1 for a clearer illustration thereof;

Figure 3 is an enlarged sectional View through a multi-band coil assembly of the amplifier of Figure l;

Figure 4 is a top View of one physical structure embodying the present invention, with the wiring connections omitted;

Figure is a front view of the structure of Figure 4;

Figure 6 is a side view of the structure of Figure 4; and

Figures 7, 8 and 9 are enlarged side, top and front views, respectively, of the tube holding movable member of the unit of Figure 4.

Referring now to Figure 1, there is illustrated an amplier for high frequencies which isA contained within and mounted in a` shielding housing or chassis symbolically illustrated at I6. There are illustrated support or mounting members, some of which are fixed relative to the chassis l0, the others of which are movable relative thereto. Each of the xed mounting members are distinguished by the broken lines at the top ends thereof, as viewed in the said Figure 1, symbolically signifying attachment to said chassis. Beginning at the left hand end of Figure 1, the members are as follows: II fixed, I2 movable, I3 fixed, Ill xed, I5 movable, I6 iixed, I'I movable, I8 fixed, I9 movable, ,28 xed, 2| fixed, 22 movable, and 23 xed. The movable members are arranged to slide between the fixed members in unison, and for this purpose all are interconnected for gang movement, as indicated symbolically by the broken line 24|. In this View, the members all appear as strips of insulating material arranged side by side, slidable, longitudinally of one another. This is merely symbolic, however, since the members may be of any suitable shape or size, may be slidable in any manner, either rectilinearly, circularly, or arcuately, and said members may be arranged as coaxial wafers' or discs, or tiers. Obviously there is means for guiding and conning the paths of the movable members, but these are not deemed necessary of illustration.

The illustrated circuit has three different positions for the movable members, namely, the Band 1 position, the Oif position, and the Band 2 position. In the Band 1 position, which is illustrated in the drawing, the lower of the tuned circuits is being utilized, in the Off position the entire amplifier is by-passed, and in the Band 2 position the uppel` of the tuned circuits is utilized. Obviously the number of positions may be increased in the event the number of bands and tuned circuits are increased.

The input to the amplifier is obtained by connecting and appropriately matching the same to the input or antenna leads 36 and 3|. The input lead 30 extends to contact terminals 35 and 36 on the member II, which extend into the path of wiper contacts on the movable member I2, on the left hand side thereof. The input lead 3l extends to contact terminals 4|] and 4| which also extend into the path of wiper contacts on the movable member l2, albeit on the right hand side thereof.

The output of the amplifier is by way of output leads 42 and 43 which may be connected to the input of a television receiver. The lead l2 extends to contact terminals Il and 48 on the member 2| and are in the path of wiper contacts on the movable member 22, on the left hand side thereof. The lead 43 extends to contact terminals 52 and 53 which also are on the member 2| and are in the path of wiper contacts on the movable member 22, albeit on the right hand side thereof.

The xed members and I3 carry juxtaposed contact terminals 55 and 56, respectively, while the fixed members 2| and 23 carry similar contact terminals 51 and 58, respectively. The con- 4 tact terminals 55 and 56 are connected by the lead 59 while the contactterminals 56 'and 5l are connected by the lead 66.

A Band 1 input transformer 6| ismounted on the bottom portion of the xed member HI and consists of a primary 62 and a secondary 63 and a` movable magnetic core 61| as of powdered iron. The .primary 62 is connected across contact terminals 65 and 66 mounted respectively upon the fixed members Il and I3. The secondary 63 is connected to contact terminals 61 and 68 which extend into the path of and are engaged by contacts on the movable member I5 on the left hand side thereof. The Band 2 input transformer l0 is also mounted on the xed member Iii and consists of a primary l| and a secondary l2. As will be explained, both transformers 6| `and 'IU are tuned by means of the same iron core. The primary 'II is connected across terminals 'I3 and 14, on the members il and I3 respectively, while the secondary 'I2 is connected to terminals 'I5 and 'I6 on the member III.

Output transformers VI and 'I8 of Band 1 and Band 2 respectively are located on the fixed member 20 and are arranged and constructed in the same manner as are transformers 6I and it. Thus transformer 'I'I has primary 13, secondary 30, and an iron core 8|. The iron core 8| is used also to tune the output transformer 78. The primary 19 is connected to contact terminals 82 and 83 on the member 2|), and the secondary 86 is connected to contact members and 86 on fixed members 2| and 23 respectively. The transformer 18 similarly has a primary 3l, and a secondary 88 connected to contact terminals 90 and 9| on the member 26 and contact 92' and 93 on the members 2| and 23 respectively.

The movable member includes a vacuum tube socket formed in the member Il itself and upon which a vacuum tube |06 is mounted. The tube |63 is a pentode. The electrodes of the tube |06 are the plate ||J|, suppressor grid |62, screen grid |03, control grid |04, cathode |65, and lament |66. As is common, the suppressor grid |62 is shown connected toy the cathode |05. Plate supply power is indicated by positive leads` III) and which connect with contact terminals ||2 and |I3 on the stationary member I8, that Lare selectively engaged by a contact making member |36 on the movable member I'I. The negative plate supply is indicated by the leads H5 and H6 which are connected with contact terminals Ill and ||8 respectively that are mounted on xed member I6 and are engaged by a contact making member |32 on the movable member I1 in its alternate positions. The terminals I I5 and I I6 likewise serve as the negative `of the filament power supply, the positive thereof being indicated by the leads H9 and |23 and connected respectively to contact terminals I2! and |22 which are on the member I6 and engaged by a Contact making member |26 on the movable member |I in its alternate positions.

The positive side of the lament |06 is connected by lead |25 to the contact strip |23 on the left hand edge of the movable member Il. The negative side of the filament |06 is connected to a ground terminal |21. The cathode |35 is also at ground potential by reason of lead |23. Another ground is conveniently placed at |29, same being connected by lead |38 to ay grounded shield I3| and contact strip |32 on left hand edge of member II. The member |'I carries a screen resistor |33 and its by-pass condenser |341 con- 5, nected to ground at |29, and the filter condenser |35. The screen grid resistor |33 is connected to the contact strip |35 on the right hand edge of member I7. The grounded terminal |27 is connected by a tube input lead |38 to a contact strip |39 on the left hand side of the movable member I5. The control grid |04 is connected to terminal |40 which in turn is connected by the input ground lead |4I to contact strip |42 on left hand side of the member I5. The plate IUI is connected by tube output lead |43 to a contact strip |44 on the right hand edge of movable member |9. The contact strip |36 and the contact strip |45 are connected together by an output ground lead |46, the strip |45V being located on the right hand edge of the movable member I9.

The input circuit of the tube |36 comprises the two leads |38 and |4I, while the output circuit of the tube IBD consists of the two leads |43 and |45. Since the members I5, I7, and i9 move in unison, these leads can be made extremely short, and will move with the tube IUU The principal advantages of my invention evolve from this feature thereof. Since the leads of the input and output circuits of the tube are extremely short, yet are permanently secured to the movable member I7, the shunt capacitance of the` leads to ground and between wires is decreased thereby increasing the gain and band width of the amplier. Likewise, the production of the device is simpliiied because it is an easy matter to provide the connections and short leads depicted.

An explanation of the operation or" the device will now be given. Each of the members I2, I5, I7, |9 and 22 is adapted to slide back and forth to any one of three positions. The position of the ganged members controls the resulting circuit. In Figure 1 the position illustrated is Band l in which the amplifier is arranged to amplify the frequencies occurring in a band capable of being passed by the transformers 6| and 77. The member I2 has elongate contact strips |511! and |I along the left h and edge and the similar strips |52 and |53 on the right hand edge, said strips being spaced one from the other in a manner to provide the necessary circuit establishing contact. The member 22 carries similarly positioned and constructed Contact strips |54, |55, 56 and I 57.

In the position shown, the input circuit leads 3S and 3| are connected to the primary 62 via the contact strips |51! and |52, respectively. The contact terminals throughout the entire ampliner are arranged to wipe the contact strips on the edges of the movable members to establish electrical engagement therewith. The secondary 63 of the transformer 6I is connected tothe input of the tube IOIJ via the contact strips |39 and |42, and the conductors |38 and |4 I.

The output circuit of the tube |00 feeds into the primary 79 of the transformer 77 in the following manner: plate I|i|, lead |43, contact strip |44, contact terminal 82, primary 79, contact terminal 83, lead |45, contact strip |36, contact terminal |I2 to positive plate power lead IIB. The secondary 80 of the transformer 77 is connected to feed its output to the output leads 42 and 43 via the contact terminals 85-8'5 and contact strips |54 and |56 and contact terminals 47 and 52.

In the Band l position described, the tube |00 obtains its operating voltages in the following manner: positive iilament voltage terminal ||9, contact terminal I2I, contact strip |26, lead |25, filament |96, ground terminal |27. The negative plate power and filament voltage terminal ||7 which may be considered at ground potential is connected to the contact terminal |I 7, contact strip |32, and thence to the terminal 23 which is at the same ground potential as the cathode |95 and the terminal |27. Obviously, if there are biasing networks in the cathode circuit, or similar biasing circuit components, these are readily mounted close to the tube ISB and its terminals in the same manner that the screen grid components |33, |34, and |35 are mounted, namely, upon the member |7, and with extremely small leads.

As thus described, the amplifier is arranged so that the transformers 6I and 77 are utilized. The cores 64 and 8| of these transformers are ganged together as indicated at It!) so as to tune them simultaneously.

The next position reached by moving the members |2, I5, I9, and 22 upward is the off position where the preamplifier is by-passed. In this position the contact strips |53 and |52 have left the terminals` 35 and 4|. The contact strips |5| and |53 now bridge the contact terminals 55-36 and .5S-4U respectively. In the same manner, contact strip |54 bridges contact terminals 47 and 57 While the contact strip |55 bridges terminals 52 and 58. Thus in the 01T position the entire ampliiier is by-passed. The circuit connections are as follows: antenna lead 3B, contact terminal 35, contact strip 65|, contact terminal 55, lead 59, contact terminal dS, contact strip |55, contact terminal 52 to output lead 43; and lead 3|, contact terminal 4t, contact strip |53, Contact terminal 56, lead 63, contact terminal 57, contact strip |54, Contact terminal 47, and output lead 42. In this position the contact strips |26 and |36 are free of any Contact terminals so that no power is being supplied to the tube |03.

If the movable members are new siided to their uppermost positions along their respective paths the Band 2 position is reached. In this position the input of the amplifier is connected to the primary of the transformer 'it the secondary of which feeds into the tube |62, and the output of the tube |63 is fed through the primary of the transformer 78 the secondary of which is connected to the output side of the preamplifier.

In the Band 2 position the input leads and 3| are connected to supply the input to the tube |00 through the transformer 7S by the following circuits: lead 30, juncture contact terminal 36, contact strip I5 I, contact terminal 73, primary 7|, Contact terminal 74, contact strip |33, contact terminal 46 to lead 3|. The secondary 72 is connected through the contact terminais 75 and 76 and contact strips |33 and to the tube input leads |33 and III. On the opposite side of the tube the output leads |43|4|=3 are connected through the contact strips Idilto the terminals Sill- 9| of the primary 87 of the output transformer 78. The secondary of this transformer is connected to the output leads 42--43 by the strips |55 and |57 that bridge the terminals 92-48 and 93--53 respectively.

The tube IIl receives its supply voltages in position Band 2 over the following circuits: the screen grid voltage is derived from terminal ||3 to contact strip |36; positive filament voltage terminal |22 to contact strip |26. The ground pctential contact strip |32 is in engagement with the negative lament and plate power terminal ||8.

From the above it should be seen that the leads which connect the transformers to the tube |99 are short at any position of use of said transformers, and that under all circumstances, even the power leads of the tube may be made ei;- tremely short.

It is also desired to point out that my invention is applicable to amplifiers designed to pass a number of bands greater than two so that more than the positions described are possible.

I have found it a relatively simple matter to shield the important components of the amplifier one from the other. Thus, the input and output halves are shielded by a metallic plate shield |10 which is grounded to terminal |21, and the transformers of the two bands are shielded by a shielding plate |1I which is electrically connected to ground terminal |21 or any other suitable ground in any desired manner. The shielding is illustrated symbolically by means of broken lines.

It has been pointed out that the cores of all transformers are secured to move together by any suitable ganging device |60, so that the transformers may be tuned in pairs. In practice the core 54 tunes the input transformers 9I-19 of the respective bands, while the core 9| tunes the respective output transformers 'IS-19. Thus only one core is needed to tune the respective input transformers one a a time, and one core is needed for the respective output transformers. The construction which makes this possible is shown in Figure 3. I have shown transformers 6I and 10 both wound upon the same sleeve or coil form |80. The ends of the form may be of different diameters, as shown, in order to vary the influence of the core upon the transformer. In this case, the two ends are separated by the shielding member I1I. The primary and secondary of each transformer is closely coupled with its mate, as shown, and the respective windings may be separated by spacers ISB and 594.

The coil form |80 is provided with a cylindrical bore or passageway |85 which extends throughout the extent thereof. Disposed in the passageway is a piston-like powdered iron core 04 mounted upon an actuating rod |01 and movable longitudinally of the passageway. The construction of the two output transformers is the same as that of the input transformers, and the actuating rods of the input and output transformers are connected together for simultaneous movement.

When the amplifier is operating in Band l position, the cores are disposed, as shown in the drawing, adjacent the transformers 6I and 11 and tuning of the transformers is achieved by incremental movements of the cores relative to the said transformers. If the amplier is switched to Band 2, then the cores are bodily moved to the right as viewed in Figure 3 until they are adjacent transformers and 18, and thereafter said transformers are tuned by incremental movements of the cores.

Reference may now be had more particularly to Figures 4 through 9 that show one particular physical construction embodying the present invention. The stationary members II, I3, Id, I9, IB, 20, 2| and 23 consist of strips of insulation extending between and secured to two sheet metal end plates or brackets I90-|9I. The four strips II, I3, I4, and I0 which are of the input circuit are all on one side of the unit and the remaining strips which are of the output circuit are arranged on the opposite side of the unit, the arrangements on the two sides being symmetrical. The strip I4 is immediately below the strip I6 and is suspended therefrom by studs |92, being spaced apart by suitable tubular spacers |93 that surround the studs between the strips I4 and |6. The strips II and I3 are both in the same plane, towards the bottom of the unit, and receive the longitudinally slidable strip I2 between them. The movable strips i5 and I9 are really one single wide strip which is suspended from the strip I1 by a pair of studs |94 and suitable tubular spacers |95. In the space between the upper strip I1 and the lower strips I5 and I9 are mounted the impedance accessories for the vacuum tube amplifier including the condenser |36 (Fig. l) and the resistance there shown. The strip I1 is provided with a circular tube receiving opening under which is mounted a vacuum tube socket |91 having seven holes |96 for receiving corresponding pins on the base of the vacuum tube. 'Ihe stationary strips I8, 20, 2| and 253 are mounted symmetrically with respect to the corresponding strips I6, I4, I3 and II. The interconnected strips I1, I5 and I9 are slidable between the strips |6-I4 on one side and the strips I8-20 on the other side. The contact strips |29 and |32 ride on the upper surface of the strip I6 and selectively engage the contacts II1, H9, IIS and |20 on the upper surface of the strip I6. The contact strips |39 and |49 (Fig. l) are mounted on the under side of the strip I5 and engage corresponding contacts on the under side of the strip I4. The contact making arrangement on the output side of the unit is the same as on the input side.

The shield |10 is a metal plate extending between and connected to the brackets I90-I9|. This plate also performs the function of the shield I3I of Figure l. The bottom of the strips |5-I9 is provided with a Contact shoe |90 that slides on the top of the shield |19 (Fig. 5) and thus brings the ground connection to the movable socket assembly. The grounding shield I1I is a metal plate at right angles to the shield |10. The coil forms extend between the brackets |-I9I and through the shield I1I.

From the above description it is apparent that the assembled movable members I5, I1 and I9 constitute the movable member of a switch for switching a vacuum tube amplifier from one tunable circuit to another and that the vacuum tube amplifier is mounted directly upon the movable part of the switch. This very substantially reduces the necessary lengths of the conductor leads, thus substantially reducing the production of extraneous noise.

In compliance with the requirements of the patent statutes I have here shown and described a preferred embodiment of my invention. It is, however, to be understood that the invention is not limited to the precise construction here shown, the same being merely illustrative of the principles of the invention. What I consider new and desire to secure by Letters Patent 1. A radio frequency amplifier for amplifying in different frequency ranges including input terminals, output terminals, a number of tuning circuits for the respective frequency ranges all located at the input terminal side of the amplifier, a second and corresponding number of tuning circuits for the same frequency ranges all located at the output terminal side of the amplifier, means forming an amplifying vacuum tube socket, and switching means for establishing circuit connections from the input to the output terminals through the socket and selectively through any of the first mentioned tuned circuits in series with a corresponding one of the second mentioned tuned circuits, said switching means including a moving switch assembly, the means forming said vacuum tube socket being on the moving switch assembly.

2. A radio frequency amplifier for amplifying in different frequency ranges including input terminals, output terminals, a number of tuning circuits for the respective frequency ranges all located at the input terminal side of the amplifier, a second and corresponding number of tuning circuits for the same frequency ranges all located at the output terminal side of the amplifier, means forming an amplilng vacuum tube socket, and switching means for establishing circuit connections from the input to the output terminals through the socket and selectively through any of the first mentioned tuned circuits in series with a corresponding one of the second mentioned tuned circuits, said switching means including a moving switch assembly, the means forming said vacuum tube socket being on the moving switch assembly, and impedances for producing the required direct current and radio frequency impedances for the vacuum tube socket, said impedances being mounted on the moving switch assembly.

3. A high frequency amplifier stage having a chassis, input leads, output leads, a plurality of tunable circuits each circuit being adapted to pass frequencies of a different band and each circuit being mounted on the chassis, common variable tuning means for the respective circuits, an electron discharge tube socket, means movably mounting the socket on the chassis and arranged selectively to be positioned in close proximity to any desired one of said circuits, electrical contact terminals for the socket and mounted for movement therewith, each circuit having a set of terminal contacts in a position to be engaged by the socket contact terminals when the socket is positioned relative thereto for coupling the respective circuit therewith.

4. In combination, a first wave band input transformer, a second wave band input transformer, permeability means for variably tuning the two transformers selectively, a first wave band output transformer and a second wave band output transformer, and permeability means for variably tuning the two output transformers selectively, grounded shielding means between the input and the output transformers, grounded shielding means between the two input transformers, grounded shielding means between the two output transformers, a radio frequency amplifier, a support for the amplifier and means for moving the amplifier support from a rst position between the input and output transformers of the nrst band to a second position between the input and output transformers of the second band selectively and means for connecting the amplifier in circuit with the respective transformers between which it has been positioned.

5. In combination, a first wave band input transformer, a second wave band input transformer, permeability means for variably tuning the two transformers selectively, a first wave band output transformer and a second wave band output transformer, and permeability means for' variably tuning the two output transformers selectively, grounded shielding means between the input and the output transformers, grounded shielding means between the two input transformers, grounded shielding means between the two output transformers, a first structure on which the respective transformers are mounted, switch contacts on said structure and terminating the respective transformers, a second structure having switch contacts cooperating with the switch contacts on the first structure, means for moving the two structures relatively to effect different connections between the switch contacts of the two structures, circuit modifying means on the second structure, and circuit connections between the modifying means and the contacts of the second structure.

5. in combination, a first wave band input transformer, a second wave band input transformer, each of the two input transformers having spaced axially aligned transformer coils, a magnetic core movable selectively in the coils for variably tuning the two transformers selectively, a first wave band output transformer and a second wave band output transformer, each of the two output transformers having spaced axially aligned transformer coils, a magnetic core movable selectively in the output transformer coils for variably tuning the two output transformers selectively, grounded shielding means between the input and the output transformers, grounded shielding means between the two input transformers, grounded shielding means between the two output transformers, a first structure on which the respective transformers are mounted, switch contacts on said structure and terminating the respective transformers, a second structure having switch contacts cooperating with the switch contacts on the first structure, means for moving the two structures relatively to effect different connections between the switch contacts of the two structures, circuit modifying means on the second structure, and circuit connections between the modifying means and the contacts of the second structure.

7. In combination, a first wave band input transformer, a second wave band input transformer, a single magnetic core movable selectively in the magnetic fields of the two transformers for variably tuning the two transformers selectively, a first wave band output transformer and a second wave band output transformer, a

single magnetic core movable selectively in the magnetic fields of the output transformers for variably tuning the two output transformers selectively, grounded shielding means between the input and the output transformers, grounded shielding means between the two input transformers, grounded shielding means between the two output transformers, circuit modifying means connecting the input and output transformers of the first band and of the second band selectively, a first structure on which the respective transformers are mounted, switch contacts on said structure and terminating the respective transformers, a second structure having switch contacts cooperating with the switch contacts on the first structure, means for moving the two structures relatively to effect different connections between the switch contacts of the two structures, the circuit modifying means being mounted on the second structure, and circuit connections between the circuit modifying means and the contacts of the second structure.

8. In combination, a first wave band input transformer, a second wave band input transformer, each of the two input transformers hav- 1ng spaced .axially aligned transformer coils, a

ond wave band output 1lmagnetic core movable selectively in the coils for variably tuning the two transformers selectively, a rst wave band output transformer and a sectransformer each of the two output transformers having spaced axially aligned transformer coils, a magnetic core movable selectively in the output transformer coils for variably tuning the two output transformers selectively, grounded shielding means between the input and the output transformers, grounded shielding means between the two input transformers, grounded shielding means between the two output transformers, circuit modifying means, and means for connecting the modifying means between the input and output transformers of the first band and of the second band selectively, a first structure on which the respective transformers are mounted, switch contacts on said structure and terminating the respective transformers, a second structure having switch contacts cooperating with the switch contacts on the first structure, means for moving the two structures relatively to effect different connections between the switch contacts of the two structures, the circuit modifying means being mounted on the second structure, circuit connections between the circuit modifying means and the contacts of the second structure, the second structure and one of said grounded shielding means on the rst structure having cooperating sliding contacts for maintaining a ground connection between the two relatively movable structures.

9. A high frequency amplifier stage adapted to be interposed in an electrical circuit, and including a chassis, an amplifying electron discharge tube socket having input and output connections, said stage having separate tuned circuits for each of a number of different frequency bands, means for selecting each band with connections for associating each of said circuits with the tube socket, means for moving the tube socket relative to the chassis to positions along a predetermined path, and said input and output connections having contact terminals movable with said socket, said tuned circuits being on the chassis one adjacent each of said positions and the connections of each of said tuned circuits having contact terminals adapted cooperatively -to engage with the said first mentioned contact terminals when said socket has been moved to the corresponding position whereby to provide amplification of only the frequency band corresponding to the selected tuned circuit means.

10. Apparatus of the class described comprising a chassis, an electron discharge tube socket, and a plurality of tunable circuits mounted on the chassis each adapted to pass a frequency band, `and each having a group of electrical contact terminals adapted to enable said vacuum tube socket to be connected therewith, a mounting member for said socket movable relative to the chassis and having contact terminals connected with the electrical parts of the socket, means for moving said mounting member selectively to any one of a plurality of positions bringing the associated contact terminals thereof into proper engagement with the respective contact terminals of a predetermined one of said circuits, and means for supplying proper operating voltages to the said socket at all positions.

1l. In a high frequency multiband amplifier, a chassis, input leads mounted on the chassis, a plurality of tunable band pass circuits mounted kon the chassis each having a primary and a sec- 12 ondary, an electron discharge tube, means fixedly secured to the chassis adapted to supply operating d. c. voltages to said tube, sliding means mounting said tube, means for moving said slidable means to any one of a plurality of stations, said slidable means having contact terminals connected with the tube electrodes and adapted selectively to be positioned at any one of said plurality of stations each corresponding to a different frequency band, said d. c. Voltage supplying means and the input leads having contact terminals at each Vofsaid stations, the circuits each having its contact terminals at a different station, and slidable contact carrying switch means ganged for simultaneous movement with said tube mounting means whereby at any selected station said input leads will b e connected with one primary, while,v the associated secondary will be connected in input relationship with the tube, and the d. c. voltage supplying means will be connected with the tube.

12. In combination, a first wave band input transformer, a second wave band input transformer, a single magnetic core movable selectively in the magnetic fields of the two transformers for variably tuning the two transformers selectively, a first wave band output transformer, a second wave band output transformer, a single magnetic core movable selectively in the magnetic fields of the two output transformers for variably tuning the two output transformers selectively, grounded shielding means between the input and the output transformers and means for establishing circuit connections between the output sides of the input transformers and the input sides of the output transformers.

13. 1n combination, a first wave band input transformer, a second wave band input transformer, a single magnetic core movable selectively in the magnetic fields of the two transformers for variably tuning the two transformers selectively, a first wave band output transformer, a second wave band output transformer, a single magnetic core movable selectively in the magnetic fields of the two output transformers for variably tuning the two output transformers selectively, grounded shielding means between the input and the output transformers, and means for establishing circuit connections between the output sides of the input transformers and the input sides of the output transformers, said circuit connections including a radio frequency amplifier and switching means for connecting the amplifier between the two rst wave band transformers or the two second wave band transformers selectively.

14. Electrical band switching apparatus for selectively inserting a plurality of frequency-banddetermining elements in a circuit including an electron discharge device, comprising a stationary chassis support means for supporting said frequency-band-determining elements; a movable support member for carrying said electron discharge device; means constituting a source of energizing voltage for said discharge device on said chassis support means; a first set of contact terminals movable with said movable support member and connecting directly with the electrodes of said electron discharge device; a plurality of stationary contact terminals on said stationary chassis support connecting with said frequency-band-determining elements and the source of energizing voltage for said electron discharge device; said stationary and movable terminal contacts being arranged for engaging relationship to progressively connect different frequency-band-determining elements with saidI electron discharge device as said movable support member is progressively moved relative to said chassis support means and to connect the said source oi energizing voltage to said electron discharge device in each band position.

15. High frequency band switching apparatus comprising a stationary chassis support means having a plurality of opposed panel members forming respective elongated slots therebetween, respective movable support members slidably disposed in said slots, means for simultaneously moving said support member in said slots, cooperating terminal contact members mounted along contiguous sides of said chassis and movable support members, frequency-band-determining elements supported on said stationary chassis means, electron discharge device means supported on at least one of said movable support members, means connecting the electrodes of said electron discharge device and the frequency-band-determining elements to appropriate contact terminals on the associated supporting member, said terminal contact members cooperatively arranged to progressively connect said respective frequency-band-determining elements to appropriate electrodes of said electron discharge device as said movable members are progressively moved in said slots.

16. The combination of claim 15 characterized further by a source of energizing voltage for said electron discharge device on said fixed chassis support means, means connecting said source of voltage to said electron discharge device through cooperating terminal contacts on said fixed chassis means and said movable support.

17. The combination of claim 15 characterized further by means moiuiting some of said respective opposed panel members and the removable members supported therebetween one above the other to form a compact unit.

18. Electrical band switching apparatus for selectively inserting a first and second plurality of stationary frequency-band-determining elements respectively between a pair of input conductors and the input electrodes of an electron discharge device, and also between the output electrodes of said electron discharge device and a pair of out conductors comprising a rst set of fixed contact terminals connected to said input conductors, a second set of fixed contact terminals connected to said output conductors, a third and fourth set of xed contact terminals connected respectively to the input and output of the frequency determining elements to be connected to the input electrodes of said discharge device, a fifth and sixth set of stationary contact terminals connected to the respective input and output of the frequency determining elements to be connected to the output electrodes of said discharge device, a first movable support member carrying bridging contacts thereon positioned for successive sliding engagement with said first and third set of contact terminals for connecting said input conductors successively to diierent frequency determining elements as said movable support member is moved from one position to another, a second movable support member carrying bridging contacts thereon positioned for successive sliding engagement with said second and sixth set of contact terminals for connecting said output con- 14 ductors successively to different frequency-banddetermining elements, additional :fixed contact terminals connected to a source of energizing voltage for said elec-tron discharge device, a third movable support member carrying said electron discharge device, a plurality of contact terminals movable with said electron discharge device positioned respectively for continuous sliding engagement with said contact terminals connected to said source or energizing voltage and for successive sliding engagement with said fourth and fifth set of contact terminals for connecting said electron discharge device successively to difierent frequency band determining elements, and means for moving said movable support members and movable contact members in unison whereby band switching is accomplished.

19. A compact band switching unit comprising a first pair of opposed, separated stationary support members, a iirst movable support member, means for slidably supporting said first movable support member between said first pair of stationary support members, an electron discharge device having input and output electrodes, means for mounting said electron discharge device on said rst movable support member, juxtaposed Contact terminals on the adjoining edges of said first movable support member and said stationary support members, shielding means extending at right angles from said movable support members, a iirst plurality of frequency-band-determining elements for connection to input electrodes of said electron discharge device, a second plurality of requency-band-determining elements for connection to the output electrodes of said electron discharge device, means supporting said first plurality of frequency-band-determining elements on one side of said shielding means, means supporting said second plurality of frequency determining elements on the other side of said shielding means, connecting means coupling said rst and second plurality of frequency-band-determining means respectively to the contact terminals on the nearest one cf said stationary opposed support members, means connecting said input and output electrodes of said discharge device respectively to contact terminals on opposite sides of said movable support member, said latter contact terminals positioned for successive contact with the adjacent contact terminals on said movable support member as movable support member is moved from one position to another to successively couple one of said iirst and second plurality of frequency selective elements respectively to said input and output electrodes of said electron discharge device.

WILLIAM A. CLAPS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,075,396 Keim Mar. 30, 1937 2,150,553 Koch Mar. 14, 1939 2,244,023 Sauer June 3, 1941 2,505,862 Kallman May 2, 1950 2,555,520 Torre June 5, 1951 FOREIGN PATENTS Number Country Date 390,348 Great Britain Apr. 6, 1933 

